Callback pattern and callback hell in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a callback function that logs a message.

Node.js

function greet(name, [1]) {
  console.log('Hello ' + name);
  [1]();
}

Drag options to blanks, or click blank then click option'

Aevent

Bpromise

Casync

Dcallback

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'promise' or 'async' as a parameter name instead of 'callback'.

Not calling the callback function inside the main function.

The callback function is passed as an argument and called inside the main function.

2fill in blank

medium

Complete the code to call a function with a callback that logs 'Done'.

Node.js

function doTask(cb) {
  setTimeout(() => {
    console.log('Task complete');
    [1]();
  }, 1000);
}
doTask(() => console.log('Done'));

Drag options to blanks, or click blank then click option'

Acb

Bcallback

Cdone

Dfinish

Attempts:

3 left

💡 Hint

Common Mistakes

Calling a function name not defined as a parameter.

Forgetting to call the callback function.

The callback function passed as 'cb' is called after the task finishes.

3fill in blank

hard

Fix the error in the nested callbacks to avoid callback hell.

Node.js

function step1(cb) {
  setTimeout(() => {
    console.log('Step 1');
    cb();
  }, 500);
}

function step2(cb) {
  setTimeout(() => {
    console.log('Step 2');
    cb();
  }, 500);
}

step1(() => {
  [1](() => {
    console.log('Step 3');
  });
});

Drag options to blanks, or click blank then click option'

Acallback

Bstep2

CsetTimeout

Dstep1

Attempts:

3 left

💡 Hint

Common Mistakes

Calling 'step1' again inside its own callback causing infinite loop.

Using undefined function names.

To avoid callback hell, call the next step function properly inside the previous callback.

4fill in blank

hard

Fill both blanks to create a nested callback structure that logs steps in order.

Node.js

function first(cb) {
  setTimeout(() => {
    console.log('First');
    [1]();
  }, 300);
}

function second(cb) {
  setTimeout(() => {
    console.log('Second');
    [2]();
  }, 300);
}

first(() => {
  second(() => {
    console.log('Done');
  });
});

Drag options to blanks, or click blank then click option'

Acb

Bcallback

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for callback parameters inconsistently.

Not calling the callback functions inside setTimeout.

Both functions call their callback parameter to continue the chain.

5fill in blank

hard

Fill all three blanks to create a callback chain that logs three steps in order.

Node.js

function one(cb) {
  setTimeout(() => {
    console.log('One');
    [1]();
  }, 200);
}

function two(cb) {
  setTimeout(() => {
    console.log('Two');
    [2]();
  }, 200);
}

function three(cb) {
  setTimeout(() => {
    console.log('Three');
    [3]();
  }, 200);
}

one(() => {
  two(() => {
    three(() => {
      console.log('All done');
    });
  });
});

Drag options to blanks, or click blank then click option'

Acb

Bcallback

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing callback parameter names inconsistently.

Forgetting to call the callback in any function.

Each function calls its callback parameter to continue the chain.